1. Field of the Invention
The present invention relates to a power supply and a driving method thereof and an apparatus and method for driving an electroluminescence display device using the same, and more particularly to a power supply that is adaptive for improving energy conversion efficiency and a driving method thereof and an apparatus and method for driving an electroluminescence display device using the same.
2. Description of the Related Art
Recently, the application of a power supply becomes more activated in factory automation equipments, office automation equipments, information devices, communication devices and power system, wherein the power supply is stable and capable of enabling them to be made smaller and lighter.
Generally, a switching power supply has two main parts of a rectifier to convert AC input into DC and a DC-DC converter to stabilize the DC input therefrom in regard to load fluctuation and the change of input voltage. A capacity input type of rectifying circuit, which is mainly used as a DC supply for various electronic devices, needs a capacitor of big capacity in order to reduce the burden of the device by restraining the input voltage fluctuation of the DC-DC converter.
Referring to FIG. 1, a prior art power supply and a driving apparatus using the same includes a voltage boosting type of DC-DC converter 10 to receive DC power source Vin for boosting it to a desired output voltage and a driving apparatus 20 to receive the boosted output voltage from the DC-DC converter 10 for being driven.
The voltage boosting type of DC-DC converter 10 controls the on/off ratio of a switching device (not shown) to boost the voltage of the DC power source Vin, thereby outputting the boosted DC power source Vin. At this moment, the voltage boosting type of DC-DC converter 10 uses a pulse width modulation method in case that the output current is high and a pulse frequency modulation method in case that the output current is low, in consideration of energy conversion efficiency.
Generally, a method by the voltage boosting type of DC-DC converter 10 has a disadvantage that it is not easy to be realized in real because the on/off ratio should be controlled on a large scale whether it is the pulse width modulation method or the pulse frequency modulation method in order to boost the output voltage more than three or four times in comparison with the input voltage. Further, the on/off ratio cannot be set to be more than 80% at maximum due to the energy conversion efficiency. Accordingly, the difference between the input voltage and the output voltage of the DC-DC converter 10 is around 5 times in design, but it is 4 times at maximum in real.
On the other hand, a DC-DC converter 10 that boosts voltage in a charge pump method where several capacitors are multitier-configured, is easy to be controlled arbitrarily in accordance with the design of the output voltage, but has many limits in output current. That is, in the charge pump type of DC-DC converter 10, the efficiency of the first tier is more than 90% in output, but the efficiency rapidly falls as it goes through several tiers.